"The Holy Father has put his heart and soul into his recovery," Dr Stefano Margaritora told Vatican News, adding that he expected the pope to recover fully from surgery "in another 10 days or so".
Leo, 71, is scheduled to make an ambitious November 6-17 trip to Uruguay, Peru and Argentina, including a dozen flights and two helicopter rides to high altitudes.
"As for a long trip involving air travel in about three weeks, I would say there are no clinical reasons why it should not take place," Margaritora said on Saturday.
Leo had the lower lobe of his right lung removed on Tuesday, confirming he had adenocarcinoma, the most common type of lung cancer.
He left the hospital on Saturday, well ahead of the week-long hospital stay the Vatican had anticipated.
"I am much better, thank you," the Pope said when asked how he was.
Leo greeted patients inside the hospital, before waving to well-wishers outside.
He paused when a 13-year-old Ukrainian girl presented him with a homemade papal doll that she said had helped her through successful cancer treatment.
She had briefly met Leo at an audience in St Peter's Square in December - an encounter she told reporters "gave her the strength to overcome the illness".
Leo has shown signs of recovering well. He had a phone call with Russian President Vladimir Putin, held meetings with senior aides and celebrated Mass in a makeshift hospital chapel.
He will take on his first official duty on Sunday, delivering the traditional Angelus blessing to the faithful in St Peter's Square.
It comes exactly one week after the pontiff revealed to throngs in the square that the nodule had been found and would be surgically removed.
Margaritora also confirmed the nodule was discovered by chance during routine abdominal examinations. It appeared as "a small spot" at the base of the lung, which extends down to the diaphragm, he said.
He added that if the spot had been higher up, "it certainly would not have been seen".
The cancer was in its early stages, and the Pope had "no respiratory symptoms, and felt perfectly well", Margaritora said.
He described Tuesday's procedure to remove the lobe as "routine" and "without complications" but acknowledged that it "stirred deep feelings ... to operate on a Pope, who for the first time - at least in modern history - is undergoing surgery for a malignant tumour."
Testing of the tumour and related lymph nodes was underway. The results, along with details of the tumour's molecular and genetic makeup, will help doctors determine whether the Pope needs additional treatment. Options include chemotherapy, a combination of chemotherapy and immunotherapy, or targeted oral therapy based on the tumour's genetic characteristics.
Margaritora said the Pope's recovery so far had required "very little assistance from us".
"His determination to recover quickly has been effective in every respect. It was truly commendable."
15°C